The present invention relates to compounds that bind to and affect PPAR-alpha, PPAR-gamma, and PPAR-delta. In another aspect, the present invention relates to methods for prevention or treatment of PPAR-gamma mediated diseases and conditions, and to methods for design of antagonists of PPAR-alpha, PPAR-gamma, and PPAR-delta. In another aspect, the present invention relates to compounds that bind to and affect FXR, LXR-alpha, and LXR-beta. In another aspect, the present invention relates to methods for the prevention or treatment of diseases mediated by FXR, LXR-alpha, and LXR-beta, and to methods for the design of antagonists of FXR, LXR-alpha, and LXR-beta.
Peroxisome Proliferator Activated Receptors (PPARs) are orphan receptors belonging to the steroid/retinoid receptor superfamily of ligand-activated transcription factors. See, for example, Willson, T. M. and Wahli, W., Curr. Opin. Chem. Biol., (1997), Vol. 1, pp 235-241.
Three mammalian PPARs have been identified which are termed PPAR-alpha, PPAR-gamma, and PPAR-delta. PPARs regulate expression of target genes by binding to DNA response elements as heterodimers with the retinoid X receptor. These DNA response elements (PPRE) have been identified in the regulatory regions of a number of genes encoding proteins involved in lipid metabolism and energy balance. The biological role of the PPARs in the regulation of lipid metabolism and storage has been recently reviewed. See, for example, Spiegelman, B. M., Diabetes, (1998), Vol. 47, pp 507-514, Schoonjans, K., Martin, G., Staels, B., and Auwerx, J., Curr. Opin. Lipidol., (1997), Vol. 8, pp 159-166, and Brun, R. P., Kim, J. B., Hu, E., and Spiegelman, B. M., Curr. Opin. Lipidol., (1997), Vol. 8, pp 212-218.
PPAR-gamma ligands of the thiazolidinedione class (TZD) enhance the actions of insulin in man and reduce circulating glucose levels in rodent models of diabetes. The PPAR-gamma receptor is expressed in adipose tissue and plays a pivotal role the regulation of adipocyte differentiation in vitro. TZD such as rosiglitazone induce adipocyte differentiation in vitro through activation of the PPAR-gamma receptor. Although there are clearly therapeutic uses for PPAR-gamma ligands in the treatment of diseases of lipid metabolism and energy balance, it is possible that there will be side effects of these drugs. For example, PPAR-gamma ligands that promote adipocyte differentiation in vivo could lead to increased fat accumulation and weight gain. This side effect might offset the beneficial effects of a PPAR-gamma ligand in the treatment of diabetes or other diseases where obesity is a risk factor. See, for example, the Spiegelman and Brun articles cited above.
Essential dietary fatty acids and certain of their eicosanoid metabolites are naturally occurring hormones for the PPAR receptors (Kliewer, 1997; Kliewer 1995). These hormones can promote adipogenesis through activation of the PPAR-gamma receptor. See, for example, Kliewer, S. A., et al., Proc. Natl. Acad. Sci. USA, (1997), Vol. 94, pp 4318-4323, and Kliewer, S. A., et al., Cell, (1995), Vol. 83, pp 813-819. Molecules that inhibit the adipogenic effects of endogenous PPAR-gamma hormones may be useful in the treatment of diseases caused by increased fat accumulation or lipid storage. See, for example, Tontonoz, P., Hu, E., and Spiegelman, B. M., Curr. Opin. Genet. Dev., (1995), Vol. 5, pp 571-576. Examples of these diseases are obesity, osteoporosis, and acne. For example, it has also been noted that TZD promote adipogenesis in bone marrow and inhibit expression of markers of the osteoblast phenotype such as alkaline phosphatase. See, for example, Paulik, M. A. and Lenhard, J. M., Cell Tissue Res., (1997), Vol. 290, pp 79-87. These effects may lead to low bone mineral density and osteoporosis. Compounds that promote osteogenesis activity may be useful in the treatment of osteoporosis. Similarly, it is known that the TZDs can promote lipid accumulation in sebocytes. See, for example, Rosenfield, R. L., Deplewski, D., Kentsis, A., and Ciletti, N. Dermatology, (1998), Vol. 196, pp 43-46. These effects may lead to sebocyte differentiation and acne formation. Thus, molecules that block adipogenesis in adipocytes, pre-adipocytes, bone marrow, or sebocytes may have beneficial effects in the treatment of obesity, osteoporosis, or acne.
The PPAR-gamma receptor has been found in tissues other than adipose, and it is believed that synthetic PPAR-gamma ligands and natural PPAR-gamma hormones (natural ligands) may have beneficial effects in many other diseases including cardiovascular disease, inflammation, and cancer. See, for example, the Schoonjans article cited above, Ricote, M. et al., Nature, (1998), Vol. 391, pp 79-82, and Mueller, E. et al., Mol. Cell, (1998), Vol. 1, pp 465-470.
FXR, LXR-alpha, and LXR-beta are orphan receptors belonging to the steroid/retinoid receptor superfamily of ligand-activated transcription factors. See, for example, Repa, Joyce J. and Mangelsdorf, David J., Curr. Opin. Biotechnol. (1999), 10(6), 557-563.
There is precedent among other members of the steroid/retinoid receptor superfamily that synthetic ligands can be identified which mimic many of the beneficial effects but inhibit some of the detrimental side effects of the natural hormones. See, for example, McDonnell, D. P., Biochem. Soc. Trans., (1998), Vol. 26, pp 54-60. These synthetic ligands have been given various labels, including antagonists, anti-hormones, partial agonists, selective receptor modulators, tissue selective ligands, and others. See, for example, Katzenellenbogen, J. A., O""Malley, B. W., and Katzenellenbogen, B. S., Mol. Endocinol., (1996), Vol. 10, pp 119-131.
PPAR-alpha ligands of the fibrate class reduce circulating triglyceride levels and raise HDL. PPAR-alpha ligands may be useful for treatment dyslipidemia and cardiovascular disorders, see Fruchart, J.-C., Duriez, P., and Staels, B., Curr. Opin. Lipidol. (1999), Vol. 10, pp 245-257. Less is known about the biology of PPAR-delta ligands, although it has been reported that they raise HDL levels, see Berger, J. et al., J. Biol. Chem. (1999), Vol. 274, pp 6718-6725.
Antagonists of PPAR-alpha or PPAR-delta would be useful for characterizing the role of these receptors in mammalian physiology. For example, administration of a PPAR-alpha antagonist or PPAR-delta antagonist to a whole animal would constitute a chemical knock-out of the target receptor. Characterization of the phenotype of this chemical knock-out would indicate the role of the target receptor in mammalian physiology. This knowledge would allow the target receptor to be associated with a particular disease.
Activation of transcription by nuclear receptors involves the recruitment of coactivator proteins. Agonist ligands promote recruitment of coactivator proteins to the receptor by stabilization of the C-terminal AF-2 helix of the ligand binding domain in a conformation that forms a xe2x80x9ccharge clampxe2x80x9d, see Nolte et al, Nature (1998) and Shiau, A. K. et al., Cell (1998), Vol. 95, pp 927-937.
PPAR agonists such as thiazolidinediones, fibrates and fatty acids share a common binding mode to their receptors. Despite differences in the chemical structure of these agonists, the acidic headgroups of these agonist ligands accept a hydrogen bond from a tyrosine residue in the AF2 helix and/or a histidine or tyrosine residue in helix-5. These hydrogen bonds stabilize the charge clamp. This is a critical step in the activation of the receptor by an agonist ligand, see Xu et al., Mol. Cell (1999), Vol. 3, pp 397-403 and Oberfield et al., PNAS (1999), Vol. 96, pp 6102-6106. In PPAR-alpha these residues are Tyrosine 464 and Tyrosine 314, respectively, using the residue numbering in Genbank S74349 (translation G765240). In PPAR-gamma these residues are Tyrosine 473 and Histidine 323, respectively, using the residue numbering in Genbank X90563 (translation G1490313). In PPAR-delta these residues are Tyrosine 437 and Histidine 287, respectively, using the residue numbering in Genbank L07592 (translation G190230).
Structural studies suggest that many nuclear receptors share a similar general mechanism of activation, where binding of ligand stabilizes the AF2 helix, thereby stabilizing the charge clamp and allowing coactivators to bind. X-ray structures of the estrogen receptor, progesterone receptor, thyroid receptor, retinoic acid receptor and vitamin D receptor show that, in these cases, the ligand generally makes lipophilic contacts with the AF2 helix. In some cases, such as the estrogen receptor, these contacts are very tenuous.
The PPARs are unusual in having a tyrosine residue in the AF2 helix available to make a direct hydrogen bond with the ligand. The interaction with this tyrosine appears to be essential for full activation of the PPAR. Sequence analysis and homology modeling indicate that FXR, LXR-alpha, and LXR-beta are similar to the PPARs in having an amino acid in the AF2 helix which can form a hydrogen bond with the ligand. In human FXR, this residue is Tryptophan 469, using the residue numbering in Genbank U68233 (translation G1546084). In human LXR-alpha, this residue is Tryptophan 443, using the residue number in Genbank U22662 (translation G726513). In human LXR-beta, this residue is Tryptophan 457, using the residue numbering in Genbank U07132 (translation G641962). Homology modeling further suggests that the ligand can make a hydrogen bond with the side chain NH of this AF2 tryptophan, and that this hydrogen bond may be essential for full activation of FXR, LXR-alpha, and LXR-beta.
As used herein, a xe2x80x9cPPAR-gamma ligandxe2x80x9d is a compound that binds to human PPAR-gamma with a pKi of greater than 5 when tested in the binding assay described below. As used herein a xe2x80x9cPPAR-gamma antagonistxe2x80x9d is a PPAR-gamma ligand that gives greater than 50% inhibition of lipogenesis when tested in the adipocyte differentiation assay described below and greater than 50% inhibition of transactivation by 100 nM rosiglitazone when tested in the cell-based reporter assay described below.
As used herein, a xe2x80x9cPPAR-alpha ligandxe2x80x9d is a compound that binds to human PPAR-alpha with a pKi of greater than 5 when tested in the binding assay described below. As used herein a xe2x80x9cPPAR-alpha antagonistxe2x80x9d is a PPAR-alpha ligand that gives greater than 50% inhibition of transactivation by 100 nM 2-(4-(2-(1-Heptyl-3-(4-fluorophenyl)ureido)ethyl)phenoxy)-2-methylpropionic acid when tested in the cell-based reporter assay described below.
As used herein, a xe2x80x9cPPAR-delta ligandxe2x80x9d is a compound that binds to human PPAR-alpha with a pKi of greater than 5 when tested in the binding assay described below. As used herein a xe2x80x9cPPAR-delta antagonistxe2x80x9d is a PPAR-delta ligand that gives greater than 50% inhibition of transactivation by 1000 nM 2-(4-(2-(1-Heptyl-3-(4-fluorophenyl)ureido)ethyl)phenoxy)-2-methylpropionic acid when tested in the cell-based reporter assay described below.
As used herein, a xe2x80x9cPPAR antagonistxe2x80x9d is a compound that is an antagonist of any one, or more than one, PPAR. As used herein, a xe2x80x9cPPAR agonistxe2x80x9d is a compound that is an agonist of any one, or more than one, PPAR.
As used herein, an xe2x80x9cFXR ligandxe2x80x9d is a compound that binds to human FXR with a pKi of greater than 5 when tested in an FXR binding assay. As used herein, an xe2x80x9cFXR antagonistxe2x80x9d is an FXR ligand that gives greater than 50% inhibition of transactivation when tested in an FXR cell-based reporter assay such as that described by Parks, D. J., et al., Science (1999) Vol. 284, pp 1365-1368.
As used herein, an xe2x80x9cLXR-alpha ligandxe2x80x9d is a compound that binds to human LXR-alpha with a pKi of greater than 5 when tested in an LXR-alpha binding assay such as that described in Janowski, B. A., et al., Proceedings of the National Academy of Sciences (USA) (1999) Vol. 96, pp. 266-271. As used herein, an xe2x80x9cLXR-alpha antagonistxe2x80x9d is an LXR-alpha ligand that gives greater than 50% inhibition of transactivation when tested in an LXR-alpha cell-based reporter assay such as that described by Janowski, B. A., et al., Proceedings of the National Academy of Sciences (USA) (1999) Vol. 96, pp. 266-271.
As used herein, an xe2x80x9cLXR-beta ligandxe2x80x9d is a compound that binds to human LXR-beta with a pKi of greater than 5 when tested in an LXR-beta binding assay such as that described in Janowski, B. A., et al., Proceedings of the National Academy of Sciences (USA) (1999) Vol. 96, pp. 266-271. As used herein, an xe2x80x9cLXR-beta antagonistxe2x80x9d is an LXR-beta ligand that gives greater than 50% inhibition of transactivation when tested in an LXR-beta cell-based reporter assay such as that described by Janowski, B. A., et al., Proceedings of the National Academy of Sciences (USA) (1999) Vol. 96, pp. 266-271.
Briefly, in one aspect, the present invention discloses compounds of Formula (I) or (II), or pharmaceutically acceptable salts or solvates thereof, 
where in Formula (I) X is O, S, or NH;
and R is methyl, ethyl, n-propyl, i-propyl, cyclopropyl, n-butyl, phenyl, or xe2x80x94CH2OCH3, 
xe2x80x83where in Formula (II) X is C or N;
and R is methyl, ethyl, n-propyl, i-propyl, xe2x80x94CH2OCH3, or xe2x80x94CO2CH3. These compounds are PPAR gamma antagonists and are close analogues of PPAR gamma agonists.
In another aspect, the present invention discloses a method for prevention or treatment of a PPAR-gamma mediated disease or condition comprising administration of a therapeutically effective amount of a compound of this invention. As used herein, xe2x80x9ca compound of the inventionxe2x80x9d means a compound of formula (I) or (II) or a pharmaceutically acceptable salt, or solvate thereof.
In another aspect, the present invention discloses a method for preparation of, or design of, PPAR antagonists comprising chemical modification of a PPAR agonist or ligand to a) prevent formation of a hydrogen bond between the agonist and tyrosine or histidine involved in receptor activation, and/or to b) displace the tyrosine or histidine involved in receptor activation from their agonist bound position, wherein little or no additional modification or changes in the structure of the agonist are made. The resulting compounds are PPAR antagonists that are close structural analogues of the corresponding PPAR agonist.
In another aspect, the present invention provides PPAR antagonists prepared using the method of this invention. As used herein, an xe2x80x9cantagonist of this inventionxe2x80x9d means a PPAR antagonist, or a pharmaceutically acceptable salt, or solvate thereof, that was prepared or designed using the method of this invention.
In another aspect, the present invention provides a method for prevention or treatment of a PPAR mediated disease or condition comprising administration of a therapeutically effective amount of a PPAR antagonist of this invention.
In another aspect, the present invention discloses a method for preparation of, or design of, FXR antagonists comprising chemical modification of an FXR agonist or ligand, to a) prevent formation of a hydrogen bond between the agonist and the tryptophan residue involved in receptor activation, and/or to b) displace the tryptophan residue from its agonist bound position, wherein little or no additional modification or changes in the structure of the agonist are made. The resulting compounds are FXR antagonists that are close structural analogues of the corresponding FXR agonist.
In another aspect, the present invention provides a method for prevention or treatment of a FXR mediated disease or condition comprising administration of a therapeutically effective amount of a FXR antagonist of this invention.
In another aspect, the present invention discloses a method for preparation of, or design of, LXR-alpha antagonists comprising chemical modification of an LXR-alpha agonist or ligand, to a) prevent formation of a hydrogen bond between the agonist and where the tryptophan residue in the AF2 helix that stabilizes the charge clamp, and/or to b), wherein little or no additional modification or changes in the structure of the agonist are made. The resulting compounds are LXR-alpha antagonists that are close structural analogues of the corresponding LXR-alpha agonist.
In another aspect, the present invention provides a method for prevention or treatment of an LXR-alpha mediated disease or condition comprising administration of a therapeutically effective amount of an LXR-alpha antagonist of this invention.
In another aspect, the present invention discloses a method for preparation of, or design of, LXR-beta antagonists comprising chemical modification of an LXR-beta agonist or ligand, to a) prevent formation of a hydrogen bond between the agonist and where the tryptophan residue in the AF2 helix that stabilizes the charge clamp, and/or to b), wherein little or no additional modification or changes in the structure of the agonist are made. The resulting compounds are LXR-beta antagonists that are close structural analogues of the corresponding LXR-beta agonist.
In another aspect, the present invention provides a method for prevention or treatment of an LXR-beta mediated disease or condition comprising administration of a therapeutically effective amount of an LXR-beta antagonist of this invention.
Suitable compounds of the present invention include:
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-5-propyl-1,3,4-oxadiazole,
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol4-yl)ethoxy]phenyl}ethyl}}-5-ethyl-1,3,4-oxadiazole,
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-5-phenyl-1,3,4-oxadiazole,
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}-5-butyl-1,3,4-oxadiazole,
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-5-methyl-1,3,4-oxadiazole,
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-5-methoxymethyl-1,3,4-oxadiazole,
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-5-cyclopropyl-1,3,4-oxadiazole,
(S)-{{5-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-3-methyl-1,2,4-oxadiazole,
(S)-{{5-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-3-propyl-1,2,4-oxadiazole,
(S)-{{5-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-3-methoxymethyl-1,2,4-oxadiazole,
(S)-{{5-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-3-ethyl-1,2,4-oxadiazole,
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-5-isopropyl-1,3,4-thiadiazole,
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-5-propyl-1,3,4-thiadiazole,
(S){{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-5-methyl-1,3,4-thiadiazole,
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-5-methyl-1,3,4-triazole,
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-5-propyl-1,3,4-triazole,
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-4-ethyl-1,3-oxazole,
(S)-{{2-[1-(2-Benzoylphenyl)amino]-244-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-4-isopropyl-1,3-oxazole,
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-4-propyl-1,3-oxazole,
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-4-methoxycarbonyl-1,3-oxazole,
and pharmaceutically acceptable salts and solvates thereof.
Preferred compounds of the present invention include:
(S)-{{2-[1-(2-Benzoylphenyl)amino]-2-{4-[2-(5-methyl-2-phenyloxazol-4-yl)ethoxy]phenyl}ethyl}}-5-propyl-1,3,4-oxadiazole and pharmaceutically acceptable salts and solvates thereof.
The present invention discloses a method for preparing a PPAR antagonist through chemical modification of a PPAR agonist or ligand, where the PPAR agonist or ligand possesses a functional group that accepts a hydrogen bond from tyrosine residues and/or histidine residues within the ligand binding domain that stabilize the charge clamp. Suitable chemical modifications replace the hydrogen bond accepting functional group with a non-hydrogen bond accepting functional group. Preferably a non-hydrogen bond accepting functional group has a pKa greater than 7. Preferably the chemical modifications do not change the binding position or orientation of the ligand within the ligand binding domain, but do alter the side-chain orientation of the tyrosine residues and/or histidine residues within the ligand binding domain that stabilize the charge clamp.
Specifically, for PPAR agonists or ligands where a carboxylic acid accepts a hydrogen bond from tyrosine residues and/or histidine residues within the ligand binding domain that stabilize the charge clamp, the carboxylic acid can be replaced with a 5-membered heterocyclic group including 1,3,4-oxadiazole, 1,2,4-oxadiazole, 1,3,4-thiadiazole, 1,3,4-triazole or 1,3-oxazole. Other suitable 5-membered heterocyclic groups include 1,2,3-oxadiazole, 1,2,5-oxadiazole, 1,2,3-thiadiazole, 1,2,4-thiadiazole, 1,2,5-thiadiazole, furan, thiophene, pyrrole, pyrazole, imidizole, isoxazole, isothiazole, N-substituted tetrazoles and other 5-membered heterocyclic groups containing one or more heteroatoms selected from nitrogen, oxygen and sulfur. The 5-membered heterocyclic group may be optionally substituted with 1 or 2 groups of 1 to 10 heavy atoms selected from carbon, nitrogen, oxygen and sulfur. When the heavy atom is carbon it can be optionally substituted with 1 to 3 fluorines. Furthermore, a carboxylic acid group can be replaced with a phenyl ring or a 6-membered heterocyclic group including pyridine, pyrazine, pyridazine, pyrimidine, triazine, tetrazine and other 6-membered heterocyclic rings containing one or more heteroatoms. The phenyl or 6-membered heterocyclic group can be optionally substituted with one to three groups of 1 to 10 heavy atoms selected from carbon, nitrogen, oxygen and sulfur. When the heavy atom is carbon it can be optionally substituted with 1 to 3 fluorines.
Specifically, for PPAR agonists or ligands where the free N-H of a thiazolidinedione or oxazolidinedione accepts a hydrogen bond from a tyrosine residue within the ligand binding domain that stabilizes the charge clamp, the thiazolidinedione or oxazolidinedione can be replaced with one of the heterocyclic groups listed above. Alternatively, a thiazolidinedione or oxazolidinedione may be N-substituted with a group consisting of 1 to 10 heavy atoms selected from C, N, O and S. When the heavy atom is carbon it can be optionally substituted with 1 to 3 fluorines. Furthermore, a thiazolidinedione or oxazolidinedione can be replaced with a hydantoin optionally substituted on nitrogen with one or two groups consisting of 1 to 10 heavy atoms selected from carbon, nitrogen, oxygen and sulfur. When the heavy atom is carbon it can be additionally substituted with 1 to 3 fluorines.
The present invention discloses a method for preparing an FXR antagonist through chemical modification of an FXR agonist or ligand, where the FXR agonist or ligand possesses a functional group that accepts a hydrogen bond from the tryptophan residue in the AF2 helix that stabilizes the charge clamp. This is tryptophan 469 in the human FXR. Suitable chemical modifications replace the hydrogen bond accepting functional group with a functional group that cannot accept the hydrogen bond. Preferably the chemical modifications do not substantially change the binding position or orientation of the ligand within the ligand binding domain, but do alter the conformation of the tryptophan side-chain, or displace the AF2 helix, or otherwise permit the AF2 helix to move out of the active position, thereby destabilizing the charge clamp.
The present invention discloses a method for preparing an LXR-alpha antagonist through chemical modification of an LXR-alpha agonist or ligand, where the LXR-alpha agonist or ligand possesses a functional group that accepts a hydrogen bond from the tryptophan residue in the AF2 helix that stabilizes the charge clamp. This is tryptophan 443 in the human LXR-alpha. Suitable chemical modifications replace the hydrogen bond accepting functional group with a functional group that cannot accept the hydrogen bond. Preferably the chemical modifications do not substantially change the binding position or orientation of the ligand within the ligand binding domain, but do alter the conformation of the tryptophan side-chain, or displace the AF2 helix, or otherwise permit the AF2 helix to move out of the active position, thereby destabilizing the charge clamp.
The present invention discloses a method for preparing an LXR-beta antagonist through chemical modification of an LXR-beta agonist or ligand, where the LXR-beta agonist or ligand possesses a functional group that accepts a hydrogen bond from the tryptophan residue in the AF2 helix that stabilizes the charge clamp. This is tryptophan 457 in the human LXR-beta. Suitable chemical modifications replace the hydrogen bond accepting functional group with a functional group that cannot accept the hydrogen bond. Preferably the chemical modifications do not substantially change the binding position or orientation of the ligand within the ligand binding domain, but do alter the conformation of the tryptophan side-chain, or displace the AF2 helix, or otherwise permit the AF2 helix to move out of the active position, thereby destabilizing the charge clamp.
Specifically, for FXR, LXR-alpha, and/or LXR-beta agonists or ligands where a hydroxyl group accepts a hydrogen bond from the AF2 tryptophan residue, the hydroxyl group can be removed, moved to the position corresponding to the opposite chirality, or replaced by a methyl group, amine, or other group that fails to accept hydrogen bonds. For FXR, LXR-alpha, and/or LXR-beta agonists or ligands where an ether oxygen accepts a hydrogen bond from the AF2 tryptophan residue, the ether oxygen can be removed, or replaced by a sulfur, methylene group or other group that fails to accept hydrogen bonds. For FXR, LXR-alpha, and/or LXR-beta agonists or ligands where a carbonyl oxygen accepts a hydrogen bond from the AF2 tryptophan residue, the carbonyl oxygen can be removed, or replaced by a carbon, nitrogen, sulfur or other group that fails to accept a hydrogen bond from the AF2 tryptophan residue. For FXR, LXR-alpha, and/or LXR-beta agonists or ligands where a carboxyl group accepts a hydrogen bond from the AF2 tryptophan residue, the carboxyl group can be removed, or replaced by a 5-membered heterocyclic group, which may optionally be substituted with 1 or 2 groups of 1 to 10 heavy atoms selected from carbon, nitrogen, oxygen or sulfur. Alternatively, the carboxyl group can be replaced by a phenyl ring or six-membered heterocyclic group, or other group that fails to accept hydrogen bonds. This chemical modification will usually reduce the activation of transcription by FXR, LXR-alpha, and/or LXR-beta, and may sometimes reduce the binding affinity. If the activation of transcription is substantially reduced and the binding affinity is sufficient, then the modified compound may serve as a useful antagonist for FXR, LXR-alpha, and/or LXR-beta.
It will be appreciated by those skilled in the art that the compounds or antagonists of the present invention may be utilised in the form of a pharmaceutically acceptable salt or solvate thereof. Physiologically acceptable salts include conventional salts formed from pharmaceutically acceptable inorganic or organic acids or bases as well as quaternary ammonium acid addition salts. More specific examples of suitable acid salts include hydrochloric, hydrobromic, sulfuric, phosphoric, nitric, perchloric, fumaric, acetic, propionic, succinic, glycolic, formic, lactic, maleic, tartaric, citric, pamoic, malonic, hydroxymaleic, phenylacetic, glutamic, benzoic, salicylic, fumaric, toluenesulfonic, methanesulfonic, naphthalene-2-sulfonic, benzenesulfonic hydroxynaphthoic, hydroiodic, malic, steroic, tannic and the like. Other acids such as oxalic, while not in themselves pharmaceutically acceptable, may be useful in the preparation of salts useful as intermediates in obtaining the compounds of the invention and their pharmaceutically acceptable salts. More specific examples of suitable basic salts include sodium, lithium, potassium, magnesium, aluminium, calcium, zinc, N,Nxe2x80x2-dibenzylethylenediamine, chloroprocaine, choline, diethanolamine, ethylenediamine, N-methylglucamine and procaine salts.
It will be appreciated by those skilled in the art that reference herein to treatment extends to prophylaxis as well as the treatment of established diseases or symptoms. Moreover, it will be appreciated that the amount of a compound or antagonist of the invention required for use in treatment will vary with the nature of the condition being treated and the age and the condition of the patient and will be ultimately at the discretion of the attendant physician or veterinarian. In general, however, doses employed for adult human treatment will typically be in the range of 0.02-5000 mg per day, preferably 1-1500 mg per day. The desired dose may conveniently be presented in a single dose or as divided doses administered at appropriate intervals, for example as two, three, four or more sub-doses per day.
While it is possible that compounds or antagonists of the present invention may be therapeutically administered as the raw chemical, it is preferable to present the active ingredient as part of a pharmaceutical formulation.
Formulations of the present invention include those especially formulated for oral, buccal, parenteral, transdermal, inhalation, intranasal, transmucosal, implant, or rectal administration, however, oral administration is preferred. For buccal administration, the formulation may take the form of tablets or lozenges formulated in conventional manner. Tablets and capsules for oral administration may contain conventional excipients such as binding agents, (for example, syrup, acacia, gelatin, sorbitol, tragacanth, mucilage of starch or polyvinylpyrrolidone), fillers (for example, lactose, sugar, microcrystalline cellulose, maize-starch, calcium phosphate or sorbitol), lubricants (for example, magnesium stearate, stearic acid, talc, polyethylene glycol or silica), disintegrants (for example, potato starch or sodium starch glycollate) or wetting agents, such as sodium lauryl sulfate. The tablets may be coated according to methods well known in the art.
Alternatively, the compounds and antagonists of the present invention may be incorporated into oral liquid preparations such as aqueous or oily suspensions, solutions, emulsions, syrups or elixirs, for example. Moreover, formulations containing these compounds or antagonists may be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations may contain conventional additives such as suspending agents such as sorbitol syrup, methyl cellulose, glucose/sugar syrup, gelatin, hydroxyethylcellulose, carboxymethyl cellulose, aluminum stearate gel or hydrogenated edible fats; emulsifying agents such as lecithin, sorbitan mono-oleate or acacia; non-aqueous vehicles (which may include edible oils) such as almond oil, fractionated coconut oil, oily esters, propylene glycol or ethyl alcohol; and preservatives such as methyl or propyl p-hydroxybenzoates or sorbic acid. Such preparations may also be formulated as suppositories, e.g., containing conventional suppository bases such as cocoa butter or other glycerides.
Additionally, formulations of the present invention may be formulated for parenteral administration by injection or continuous infusion. Formulations for injection may take such forms as suspensions, solutions, or emulsions in oily or aqueous vehicles, and may contain formulatory agents such as suspending, stabilising and/or dispersing agents. Alternatively, the active ingredient may be in powder form for constitution with a suitable vehicle (e.g., sterile, pyrogen-free water) before use.
The formulations according to the invention may also be formulated as a depot preparation. Such long acting formulations may be administered by implantation (for example, subcutaneously or intramuscularly) or by intramuscular injection. Accordingly, the compounds and antagonists of the invention may be formulated with suitable polymeric or hydrophobic materials (as an emulsion in an acceptable oil, for example), ion exchange resins or as sparingly soluble derivatives as a sparingly soluble salt, for example.
The formulations according to the invention may contain between 0.1-99% of the active ingredient, conveniently from 30-95% for tablets and capsules and 3-50% for liquid preparations.
The compounds and antagonists of this invention can be prepared by standard organic chemistry as illustrated by the accompanying working examples. The following examples are set forth to illustrate the synthesis of some particular compounds of the present invention and to exemplify general processes. Accordingly, the following Examples section is in no way intended to limit the scope of the invention contemplated herein.